The present invention relates to a technique for writing data in a semiconductor integrated circuit device and especially a technique effectively applicable to stabilization of data write in a semiconductor memory, which utilizes a phase-change resistance.
Development of a phase-change memory is advanced in order to achieve a high-speed and high-integrated nonvolatile memory.
In the phase-change memory, a phase-change material called a chalcogenide material stores data by utilizing a resistance property depending on its states.
Rewriting of the phase-change resistance is performed by changing its state by applying a current thereto and generating heat. A change to a low-resistance state, which is called also a set operation, reads out the phase-change material by maintaining relatively low temperature for a sufficient period, and the above operation is performed by carrying the current within such a range that the phase-change resistance is not changed (see Non-patent Document 1: 2002 IEEE International Solid-State Circuits Conference, Digest of Technical Papers, pp. 202–203).
Also, characteristics of the phase-change resistance are described in IEEE, International Electron Devices Meeting, Technical Digest (see Non-patent Document 2: 2002 IEEE International Electron Devices Meeting, Technical Digest, pp. 923–926).
Further, a memory cell, constituted by the phase-change resistance and an N-channel MOS (Metal Oxide Semiconductor) transistor, is described in Nonvolatile Semiconductor Memory Workshop, Digest of Technical Papers (see Non-patent Document 3: 2003 Non-volatile Semiconductor Memory Workshop, Digest of Technical Papers, pp. 91–92).
Not only a high-speed ROM (Read Only Memory) but also a feasibility of nonvolatile RAM (Random Access Memory) is described in the above-mentioned Documents, and then a feasibility of an integrated memory having functions of ROM and RAM in combination is mentioned therein.
FeRAM (ferroelectric RAM) and MRAM (Magnetic RAM) as similar high-speed nonvolatile memories are also developed. In the FeRAM, it is difficult to reduce an area of a ferroelectric capacitor and reduce an area of a cell. In the MRAM, since a rate of change of its magnetic resistance is small, an amount of signals to be read out is small and it is difficult to perform a high-speed reading operation.
Meanwhile, in the phase-change memory, if an area of an electrode having the phase-change resistance is smaller, the phase-change resistance can be phase-changed with low power, so that scaling is easy to perform. Also, the phase-change resistance is changed larger than the magnetic resistance of the MRAM, so that high-speed read-out is can be achieved. For these reasons, the high-speed nonvolatile memory by the phase-change memory is expected to be achieved.